As is known, a disc of the type specified above is constituted by two coaxial portions. A first portion, the support bell, is for connection to the wheel hub of a vehicle, and the remaining, peripheral portion, the so-called braking band, is for cooperating with the disc-brake calipers to exert the braking force on the vehicle.
It is also known that, during the operation of the brakes, the friction between the pads of the brake calipers and the surface of the braking band generates a large amount of heat which has to be dissipated. The heat generated in fact causes many undesired phenomena such as, for example, the formation of cracks on the braking surface, permanent deformations after cooling, or localized changes in state which in turn lead to vibrations.
In particular, in applications on high-performance motorcars with high braking efficiency, the energy to be dissipated is very high and there is an even greater need to dissipate the heat generated during braking.
This need for increased cooling efficiency must, however be reconciled with the further need to keep the space occupied by the discs unchanged to avoid modifications to the suspension of the vehicle for which they are intended.
For this purpose, ventilated discs have undergone continuous development, particularly with regard to the number and configuration of the so-called ventilation ducts which are defined between the two plates that conventionally make up ventilated discs, and between fins which connect the two plates transversely.
For example, fins constituted by curved walls repeated at a modular frequency, in which the module itself is constituted by two fins of which one is longer than the other are known from U.S. Pat. No. 5,427,212.
The above-mentioned example of a disc-brake disc cannot ensure effective cooling such as to overcome the above-mentioned disadvantages completely.
The problem underlying the present invention is therefore that of devising a disc-brake disc which has structural and functional characteristics such as to satisfy the above-mentioned requirements and at the same time to prevent the problems mentioned with reference to the prior art.